More recent versions of these browsers, as well as for Chrome, are supported.

Google is casting this decision in terms of browser feature requirements, but it is also a security measure. Google's apps have always been aggressive in terms of exploiting advanced user web interface features and these have better and more consistent support in more recent browsers.

But newer browsers, as with software generally, consistently have fewer and less severe vulnerabilities than older ones. Even though Apple, Microsoft and Mozilla may continue to support these old versions for a time (Microsoft will continue supporting IE6 until April 2014!), Google has the leverage to free themselves from supporting the bugs and design deficiencies in these programs.

The general policy at Google will be "...to support the current and prior major release of Chrome, Firefox, Internet Explorer and Safari on a rolling basis. Each time a new version is released, we'll begin supporting the update and stop supporting the third-oldest version."